可觀察與決策樹

Question

我需要一個封裝了複雜的IAP購買樹成返回布爾觀察到一個簡單的attemptPurchase函數的函數（真 - >成功，假 - >取消，錯誤 - >任何錯誤）

但是我很難理解我如何創建這個功能，主要是因爲決定的開始是異步的。

決策樹和代碼如下=>幫助非常感謝！

// fails -> missing return function 
// but i cannot return the credit check, since the execution is different depending on the result 

func attemptPurchase(amount: Int) -> Observable<Bool>{ 

    let creditCheck = creditCheck(amount) 

    creditCheck.filter{$0}.subscribeNext{ _ in 
    return Observable.just(true) 
    } 

    creditCheck.filter{$0}.subscribeNext{ _ in 
    return confirmIAP().processIAP() 
    } 
} 

func creditCheck(amount: Int) -> Observable<Bool>{ 
    return API.creditCheck.map{$0 > amount} 
} 

func confirmIAP() -> Observable<Bool> { 
    // UI for confirming IAP 
} 

func processIAP() -> Observable<Bool> { 
    // UI for uploading IAP on my server 
} 

Answer 1

這是你如何能做到這一點：

func attemptPurchase(amount: Int) -> Observable<Bool> { 
    return creditCheck(amount) 
     .flatMapLatest { (enoughCredit: Bool) -> Observable<Bool> in 
      if enoughCredit { 
       return Observable.just(true) 
      } else { 
       return confirmIAP() 
        .flatMapLatest { (isConfirmed: Bool) -> Observable<Bool> in 
         if isConfirmed { 
          return processIAP() 
         } else { 
          return Observable.just(false) 
         } 
        } 
      } 
     } 
} 

Answer 2

從iankeen的該RxSwift鬆弛組答案：

func attemptPurchase(amount: Int) -> Observable<Bool>{ 
    return creditCheck(amount) 
     .flatMap { enough in 
      return (enough ? .just(true) : confirmIAP()) 
     } 
     .flatMap { ready in 
      guard ready else { /* failure */ } 
      return processIAP() 
     } 
}